This invention relates to a method and apparatus for wire-bonding in the production of electronic components such as light-emitting diodes and transistors, say, for connecting one electrode to another by means of a metallic wire.
FIGS. 5-10 show a wire-bonding method disclosed in Japanese Patent Publication Tokkai 60-39839 for connecting a metallic wire 6 between a first bonding part 4 on the upper surface of a diode chip 3 die-bonded to a cathode 1 of a light-emitting diode and a second bonding part 5 which is on the upper end surface of an anode 2, as shown in FIG. 5-10. This is done firstly by forming a small ball 6A at the lower end of the metallic wire 6 passing through a capillary tool 7 above the first bonding part 4 as shown in FIG. 5 and secondly by moving the capillary tool 7 downward towards the first bonding part 4 such that the ball 6A at the lower end of the metallic wire 6 is bonded to the first bonding part 4 on the diode chip 3 as shown in FIG. 6. The capillary tool 7 is raised again thereafter as shown in FIG. 7. Next, the metallic wire 6 is cut by a torch flame 8 and at the same time two small balls 6A and 6B are created at both ends parts of the severed metallic wire 6 as shown in FIG. 8. Next, the metallic wire 6 which is bonded at one end to the first bonding part 4 is bent in the direction of the second bonding part 5 as shown in FIG. 9 and the ball 6B at its free end is pressed against the second bonding part 5 by lowering a bonding tool 9 as shown in FIG. 10.
The bonding tool 9 to be used for this process is conventionally of a width W which is approximately equal to the width S of the second bonding part 5. Thus, when the metallic wire 6 is bent as shown in FIG. 9 and the ball 6B at its tip is pressed against the second bonding part 5, the ball 6B may slip away from the lower surface of the bonding tool 9 or end up somewhere other than the second bonding part 5 as shown by broken lines in FIG. 10. This may happen in part because the metallic wire 6 is not sufficiently bent. One of the methods for preventing such occurrences is to increase the width W of the bonding tool 9 in the direction of the first bonding part 4 such that the ball 6B will surely be in touch with the lower surface of the bonding tool 9. If the bonding tool 9 is thus modified, however, some of the other parts of the metallic wire 6 will tend to be bent excessively. As a result, the strength of the wire-bonding may be adversely affected or the metallic wire 6 may cause a short-circuiting.
It is therefore an object of this invention to provide a method and apparatus for wire-bonding with which the problems as described above can be eliminated all at once.
A wire-bonding method embodying this invention, with which the above and other objects can be accomplished, may be characterized as comprising the steps of bonding one end of a metallic wire to a first bonding part of an electronic component, bending the other end of this metallic wire obliquely towards a second bonding part of the electronic component, and pressing the other end downward towards and onto the second bonding part by a sloped surface which extends at least to a center part of the metallic wire and is sloping diagonally upwards towards the first bonding part. A wire-bonding apparatus of this invention is characterized as comprising a capillary tool for bonding one end of a metallic wire therethrough on a first bonding part of an electronic component by pressing downward, and a bonding tool having a lower surface which is wide enough to extend to a mid-point of the metallic wire and is sloped upwards towards the first bonding part for bonding the other end of the metallic wire on a second bonding part of the electronic component by pressing downward.
By using a method or apparatus according to this invention, the second end of the metallic wire, after its first end has been bonded to the first bonding part, can be pressed against the second bonding part dependably and the probability of the wire bending excessively when it is being pressed downward by the bonding tool can be significantly reduced.